T
E
L
KO
MNIK
A
, V
ol
.
1
7
,
No.
6
,
Dec
e
mb
er
201
9
, p
p.
2
81
2
~
2817
IS
S
N: 1
69
3
-
6
93
0
,
accr
ed
ited
F
irst
Gr
ad
e b
y K
em
en
r
istekdikti,
Decr
ee
No: 2
1/E/
K
P
T
/20
18
DOI:
10.12928/TE
LK
OM
N
IK
A
.v
1
7
i
6
.
12490
â—¼
28
12
Rec
ei
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ed
F
eb
r
u
ary
5
, 2
01
9
; Rev
i
s
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J
un
e
6
, 2
01
9
; A
c
c
ep
ted
J
u
l
y
2
,
20
1
9
A
brief re
view
:
security
issue
s
in clo
ud
c
om
pu
tin
g
and
th
eir s
olu
ti
on
s
Iqb
al
Ah
med
Dep
a
rtm
e
n
t
o
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Co
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p
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r Sc
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a
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n
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Un
i
v
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t
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Chi
tt
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4
3
3
1
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Ba
n
g
l
a
d
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s
h
*C
o
rre
s
p
o
n
d
i
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g
a
u
th
o
r,
e
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m
a
i
l
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q
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l
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a
c
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b
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u
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t
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b
a
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m
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l
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Clo
u
d
Com
p
u
ti
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s
a
s
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re
d
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c
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e
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t
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fe
c
ti
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v
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a
b
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l
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ty
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n
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g
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a
t
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c
ti
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n
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o
n
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wit
h
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ts
n
u
m
e
ro
u
s
b
e
n
e
fi
ts
,
c
l
o
u
d
c
o
m
p
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ti
n
g
b
ri
n
g
s
m
u
c
h
m
o
re
c
h
a
l
l
e
n
g
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n
g
s
i
tu
a
t
i
o
n
re
g
a
r
d
i
n
g
d
a
ta
p
r
i
v
a
c
y
,
d
a
ta
p
ro
te
c
ti
o
n
,
a
u
th
e
n
ti
c
a
te
d
a
c
c
e
s
s
,
In
te
l
l
e
c
t
u
a
l
p
ro
p
e
rty
ri
g
h
ts
e
t
c
.
Due
to
th
e
s
e
i
s
s
u
e
s
,
a
d
o
p
ti
o
n
o
f
c
l
o
u
d
c
o
m
p
u
t
i
n
g
i
s
b
e
c
o
m
i
n
g
d
i
ff
i
c
u
l
t
i
n
t
o
d
a
y
’
s
worl
d
.
I
n
th
i
s
re
v
i
e
w
p
a
p
e
r,
v
a
ri
o
u
s
s
e
c
u
ri
t
y
i
s
s
u
e
s
r
e
g
a
rd
i
n
g
d
a
ta
p
r
i
v
a
c
y
a
n
d
re
l
i
a
b
i
l
i
ty
,
k
e
y
fa
c
to
r
s
whi
c
h
a
r
e
a
ff
e
c
ti
n
g
c
l
o
u
d
c
o
m
p
u
ti
n
g
,
h
a
v
e
b
e
e
n
a
d
d
r
e
s
s
e
d
a
n
d
a
l
s
o
s
u
g
g
e
s
t
i
o
n
s
o
n
p
a
rti
c
u
l
a
r a
re
a
s
h
a
v
e
b
e
e
n
d
i
s
c
u
s
s
e
d
.
Key
w
ords
:
c
l
o
u
d
c
o
m
p
u
ti
n
g
,
c
l
o
u
d
s
e
c
u
r
i
ty
,
d
a
t
a
e
n
c
r
y
p
ti
o
n
,
d
a
ta
p
ro
t
e
c
t
i
o
n
,
d
i
g
i
ta
l
s
i
g
n
a
t
u
re
Copy
righ
t
©
2
0
1
9
Uni
v
e
rsi
t
a
s
Ahm
a
d
D
a
hl
a
n.
All
righ
t
s
r
e
s
e
rve
d
.
1.
Int
r
o
d
u
ctio
n
Cl
ou
d
c
om
pu
t
i
ng
i
s
a
s
erv
i
c
e
tha
t
i
s
i
nt
ernet
ba
s
ed
an
d
tha
t
gi
v
es
t
he
fac
i
l
i
ty
of
s
ha
r
i
n
g
c
om
pu
t
er
r
es
ou
r
c
es
al
on
g
wi
th
oth
er
de
v
i
c
es
on
us
er
de
ma
nd
.
It
i
s
a
m
ec
ha
n
i
s
m
to
en
ab
l
e
on
de
ma
nd
s
h
ared
r
es
o
urc
es
.
F
or
ex
am
p
l
e,
s
erv
er,
da
t
a
c
en
tr
e,
ne
tw
ork
s
,
s
tora
g
e
ap
pl
i
c
ati
on
s
whi
c
h
c
an
s
tor
e
da
t
a.
T
ha
t
c
an
be
g
en
erat
ed
w
i
th
mi
ni
m
um
ef
fort.
In
ad
d
i
t
i
on
,
c
l
ou
d
c
om
pu
t
i
ng
prov
i
de
s
th
e
fac
i
l
i
ty
to
t
he
organ
i
z
ati
on
s
an
d
us
ers
to
k
ee
p
the
i
r
da
t
a
on
pr
i
v
ate
or
thi
r
d
-
pa
r
ty
s
torage
l
oc
ati
on
a
nd
th
es
e
l
oc
at
i
on
s
/d
ata
c
en
tr
e
s
ma
y
be
l
oc
a
ted
f
ar
away
fr
om
u
s
er,
ma
y
be
i
n
s
om
e
oth
er
c
i
ty
or
c
o
un
tr
y
i
n
t
hi
s
w
orld
.
N
ati
on
a
l
Ins
t
i
tut
e
o
f
S
ta
nd
ard
a
nd
T
ec
h
no
l
og
y
(
NI
S
T
)
gi
v
es
t
he
c
l
o
ud
c
om
p
uti
ng
’
s
de
f
i
n
i
ti
on
as
c
l
ou
d
c
om
p
uti
n
g
i
s
a
mo
d
el
for
en
ab
l
i
ng
ub
i
qu
i
to
us
,
c
on
v
en
i
en
t,
on
-
d
em
a
n
d
ne
twork
ac
c
es
s
to
a
s
ha
r
ed
po
o
l
of
c
on
f
i
gu
r
ab
l
e
c
om
p
uti
n
g
r
es
ou
r
c
es
(
e.g
.,
n
etwo
r
k
s
,
s
erv
ers
,
s
torage
,
ap
p
l
i
c
a
ti
o
ns
an
d
s
erv
i
c
es
)
tha
t
c
an
b
e
r
ap
i
d
l
y
p
r
ov
i
s
i
on
ed
a
nd
r
el
ea
s
e
d
w
i
th
mi
ni
ma
l
m
a
na
ge
me
nt
ef
fort
or
s
erv
i
c
e
prov
i
de
r
i
nte
r
ac
t
i
on
[1,
2].
F
or
be
tt
er
un
de
r
s
ta
nd
i
ng
of
c
l
ou
d
c
o
mp
ut
i
ng
s
erv
i
c
es
,
on
e
ne
ed
s
to
c
om
preh
en
d
t
he
i
mp
orta
nc
e
an
d
c
ha
r
ac
teri
s
ti
c
s
of
c
l
ou
d s
er
v
i
c
es
whi
c
h
are ex
p
l
a
i
ne
d h
ere an
d repres
e
nte
d i
n Fi
g
ure 1 [
3]:
-
O
n
de
ma
nd
S
e
l
f
-
s
erv
i
c
e:
It
r
efe
r
s
to
the
s
erv
i
c
e
w
hi
c
h
en
a
bl
es
prov
i
s
i
on
i
n
g
of
c
l
ou
d
r
es
ou
r
c
es
to
v
en
d
ors
on
d
em
an
d
or
w
he
n
ev
er
th
ey
a
r
e
r
eq
u
i
r
ed
s
uc
h
as
ne
t
wor
k
s
torage
,
s
erv
i
c
e t
i
m
e wi
tho
ut
h
um
a
n
i
nt
erac
ti
o
n.
-
B
r
oa
d
N
etwo
r
k
A
c
c
es
s
:
S
erv
i
c
es
are
ac
c
es
s
i
bl
e
ov
er
the
ne
tw
ork
whi
c
h
are
r
etri
ev
ed
throug
h
s
om
e
s
ta
nd
ard
i
z
e
d
me
c
h
an
i
s
m
w
hi
c
h
prom
ote
s
th
e
us
a
ge
s
o
f
h
ete
r
og
en
eo
us
pl
at
forms
(
wor
k
s
tat
i
on
s
, t
ab
l
ets
,
l
ap
t
op
s
, m
ob
i
l
e p
h
on
e
s
)
.
-
Res
ou
r
c
e
P
oo
l
i
ng
:
Res
ou
r
c
es
of
c
l
ou
d
prov
i
de
r
are
p
o
ol
e
d
ov
er
the
s
erv
er.
Co
ns
um
ers
are
as
s
i
gn
e
d
d
i
ffe
r
en
t
r
es
o
urc
e
s
whi
c
h
are
e
i
th
er
p
hy
s
i
c
al
or
v
i
r
tua
l
o
ne
.
G
en
er
al
l
y
,
c
on
s
um
ers
ha
v
e
no
i
de
a
of
ex
ac
t
l
oc
ati
o
n
the
r
es
o
urc
es
prov
i
d
ed
to
th
em
ex
c
ep
t
a
t
the
ab
s
tr
ac
ti
o
n
l
ev
el
l
i
k
e s
tat
e
, c
i
ty
, c
ou
ntry
or dat
a c
en
tr
e
.
-
Rapi
d
E
l
as
ti
c
i
ty
:
S
erv
i
c
es
c
an
be
e
l
as
t
i
c
al
l
y
r
e
l
ea
s
ed
a
nd
mo
ni
t
ored
for
c
on
s
um
ers
s
erv
i
c
es
av
a
i
l
ab
l
e
to
the
m
c
an
oft
en
ap
pe
ar
as
u
nl
i
m
i
ted
w
hi
c
h
c
an
be
s
c
al
e
d
i
n
qu
a
nt
i
ty
an
y
ti
m
e.
-
Me
as
ure
d
S
erv
i
c
es
:
C
l
ou
d
s
y
s
tem
are
s
o
de
s
i
gn
ed
tha
t
th
ey
c
an
mo
n
i
tor
th
e
r
es
ou
r
c
e
us
ag
es
,
f
or
ex
a
mp
l
e
proc
e
s
s
i
ng
,
b
an
dwi
dth
an
d
ac
t
i
v
e
us
er
ac
c
ou
nts
,
s
t
orage
t
o
de
l
i
v
er
tr
an
s
pa
r
en
c
y
to
prov
i
de
r
as
wel
l
as
c
on
s
u
me
r
.
A
t
s
om
e
l
ev
el
of
ab
s
tr
ac
ti
o
n,
the
y
c
an
op
ti
mi
z
e
the
r
es
ou
r
c
e u
s
a
g
e b
y
k
ee
p
i
n
g a
c
h
ec
k
th
r
ou
gh
m
ete
r
i
ng
c
a
pa
b
i
l
i
ty
.
Evaluation Warning : The document was created with Spire.PDF for Python.
T
E
L
KO
MNIK
A
IS
S
N: 1
69
3
-
6
93
0
â—¼
A
bri
ef
r
ev
i
ew:
s
ec
uri
ty
i
s
s
u
es
i
n c
l
ou
d
c
om
p
uti
ng
an
d
t
he
i
r
s
o
l
ut
i
on
s
(
Iq
ba
l
A
hm
ed
)
2813
T
hi
s
pa
p
er
i
s
di
v
i
de
d
i
n
to
fol
l
ow
i
ng
s
ec
t
i
on
s
:
s
ec
ti
on
1
tel
l
s
ab
o
ut
th
e
i
n
tr
od
uc
t
i
on
o
f
c
l
ou
d
c
o
mp
u
ti
n
g,
s
ec
ti
on
2
gi
v
es
the
i
d
ea
of
c
l
ou
d
c
om
pu
ti
ng
m
od
el
s
wh
i
l
e
s
ec
ti
o
n
3
i
s
th
e
bri
ef
i
ntrod
uc
ti
on
of
r
el
ate
d
w
ork
s
.
S
ec
t
i
on
4
i
s
ab
ou
t
th
e
f
a
c
tors
aff
ec
t
i
ng
c
l
o
ud
c
om
p
u
ti
ng
,
s
ec
ti
on
5
i
s
the
p
os
s
i
bl
e
thre
ats
r
eg
a
r
di
ng
t
he
c
l
ou
d
c
o
mp
u
ti
n
g
pa
r
ad
i
gm
an
d
fi
n
al
l
y
s
ec
ti
o
n
6
gi
v
es
s
om
e
s
ol
ut
i
on
s
t
o t
h
e s
ec
urit
y
i
s
s
ue
s
. The c
o
nc
l
us
i
v
e rem
ark
i
s
i
n
s
ec
ti
o
n 7
.
2.
Clo
u
d
S
er
vic
e
Mod
el
s
T
he
be
n
efi
ts
an
d
i
mp
ot
e
nc
e
of
c
l
ou
d
c
om
pu
ti
n
g
mi
gh
t
be
v
ery
ap
pe
al
i
n
g
an
d
de
ma
nd
ab
l
e,
bu
t
i
t
ha
s
go
t
hu
ge
n
um
b
er
of
r
i
s
k
s
an
d
s
ec
urit
y
i
s
s
ue
s
l
i
k
e
da
t
a
l
ea
k
ag
e,
da
t
a
l
os
s
,
i
ntru
de
r
att
ac
k
s
,
ma
l
i
c
i
ou
s
i
ns
i
de
r
s
etc
.
F
o
l
l
owi
ng
s
erv
i
c
e
mo
de
l
s
are
de
f
i
ne
d
by
NIS
T
whi
c
h
i
nc
l
ud
es
t
hree c
at
eg
orie
s
[1
,
3,
4]:
-
Inf
r
as
tr
uc
ture
as
a
S
erv
i
c
e
(
Iaa
S
)
:
Iaa
S
i
s
a
l
l
ab
o
ut
pro
v
i
di
n
g
t
he
v
i
r
t
ua
l
m
ac
hi
ne
,
op
erat
i
n
g
s
y
s
tem
s
or net
wor
k
s
to
the
en
d
us
ers
. S
o
me
oth
er c
o
mp
ut
i
ng
r
es
ou
r
c
es
are
al
s
o
s
up
po
r
t
ed
i
n
I
aa
S
,
wh
ere
t
he
c
us
to
me
r
or
c
l
i
e
nt
c
an
r
un
ar
bi
tr
ary
op
erat
i
n
g
s
y
s
tem
o
n
v
i
r
tua
l
ma
c
hi
ne
or
an
y
ot
he
r
s
of
tware.
C
l
i
e
nt
c
an
c
on
tr
ol
on
l
y
t
he
op
er
at
i
n
g
s
y
s
tem
or
s
oft
war
e
w
hi
c
h
he
i
s
r
un
ni
ng
b
ut
h
e
l
os
es
hi
s
c
on
tr
ol
on
th
e
i
nfras
tr
uc
tu
r
e
whi
c
h
i
s
prov
i
d
i
n
g
h
i
m
al
l
the
s
e
s
erv
i
c
es
.
-
S
oft
w
are
as
a
S
erv
i
c
e
(
S
a
aS
)
:
I
n
th
i
s
k
i
n
d
o
f
s
c
en
ar
i
o,
us
er
i
s
on
l
y
us
i
ng
the
a
pp
l
i
c
ati
on
s
whi
c
h
are
be
i
ng
prov
i
de
d
b
y
the
v
e
nd
or
an
d
t
ho
s
e
ap
pl
i
c
a
ti
o
ns
r
un
on
th
e
c
l
ou
d
s
erv
i
c
es
.
S
am
e
ap
p
l
i
c
a
ti
o
n
i
s
ac
c
e
s
s
i
bl
e
by
ma
ny
ot
he
r
c
l
i
e
nts
as
wel
l
throu
gh
s
om
e
c
om
m
on
me
c
ha
n
i
s
m,
for
ex
am
p
l
e
b
y
us
i
ng
web
brows
er
or
e
ma
i
l
.
A
d
di
t
i
on
al
l
y
,
t
he
c
l
i
e
n
ts
or
us
ers
ha
v
e
no
c
on
tr
ol
ov
er
th
e
ap
p
l
i
c
at
i
on
or
u
nd
er
l
y
i
ng
i
nfras
tr
uc
ture,
n
etwo
r
k
s
erv
er
or
op
erat
i
n
g s
y
s
tem
up
on
whi
c
h t
he
s
e
ap
p
l
i
c
at
i
o
ns
r
un
.
-
P
l
a
tfo
r
m
as
a
S
erv
i
c
e
(
P
aa
S
)
:
In
P
a
aS
,
the
c
l
i
en
t
i
s
ab
l
e
t
o
c
r
ea
t
e
th
ei
r
ow
n
de
s
i
r
ed
ap
p
l
i
c
at
i
on
by
us
i
ng
s
o
me
progr
am
mi
n
g
l
an
g
ua
g
e,
l
i
nk
ed
l
i
brar
i
es
.
T
he
s
e
l
an
g
ua
ge
s
or
l
i
brar
i
es
are
s
up
po
r
ted
by
the
v
en
do
r
.
A
fte
r
c
r
ea
t
i
n
g
the
us
er
de
s
i
r
ed
ap
pl
i
c
ati
o
n,
i
t
i
s
de
p
l
oy
ed
on
the
s
erv
er
pro
v
i
de
d
by
th
e
v
en
do
r
.
Us
er
ha
s
al
s
o
th
e
a
uth
or
i
ty
to
c
o
nfi
g
ure
i
ts
ap
p
l
i
c
at
i
on
or
c
an
c
ha
n
ge
the
c
o
nfi
gu
r
at
i
on
s
ett
i
n
gs
l
at
er
on
.
T
he
ne
x
t
F
i
gu
r
e
2
s
ho
ws
the
r
e
l
at
i
on
s
h
i
ps
o
f th
e c
l
i
e
nts
an
d
th
r
ee
s
erv
i
c
e m
od
e
l
s
de
f
i
ne
d b
u NI
S
T
.
F
i
gu
r
e
1.
C
l
ou
d c
om
pu
t
i
ng
c
ha
r
ac
teri
s
ti
c
s
F
i
gu
r
e
2.
D
i
ffe
r
e
nt
c
l
ou
d
s
erv
i
c
e m
od
el
s
3.
Rel
ated
W
o
r
k
s
A
ga
r
w
al
A
et
al
.
h
i
gh
l
i
gh
t
the
em
erg
en
c
e
of
c
l
ou
d
c
om
pu
ti
n
g
al
o
ng
wi
t
h
i
ts
s
ec
urit
y
c
on
c
erns
l
i
k
e
da
ta
l
os
s
,
da
t
a
breac
he
s
,
i
ns
ec
ure
A
P
Is
,
ac
c
ou
nt
h
i
j
ac
k
i
ng
,
de
n
i
a
l
of
s
erv
i
c
es
[4,
5].
P
G
arg
e
t
a
l
.
ha
v
e
wor
k
ed
on
d
i
ffe
r
en
t
c
l
ou
d
s
ec
ur
i
ty
as
pe
c
ts
l
i
k
e
ba
s
i
c
s
ec
urit
y
whi
c
h
i
nc
l
ud
es
Cr
os
s
s
i
te
s
c
r
i
pti
n
g
at
tac
k
s
,
S
Q
L
i
nj
ec
t
i
on
a
tta
c
k
s
,
Ma
n
i
n
t
he
mi
d
dl
e
att
ac
k
s
[6].
P
r
ad
e
ep
K
um
ar
S
ha
r
m
a
et
al
.
a
l
s
o
wor
k
for
the
s
ec
urit
y
c
on
c
erns
of
c
l
ou
d
l
i
k
e
c
os
t
mo
de
l
c
ha
r
g
e
[6
,
7
],
s
erv
i
c
e
l
ev
e
l
ag
r
e
em
e
nts
an
d
i
s
s
ue
of
m
i
grat
i
on
s
h
ou
l
d
be
de
al
t.
Nas
e
er
A
ma
r
a
et
al
.
h
i
gh
l
i
gh
t
ed
t
h
e
s
ec
urit
y
t
hreats
,
arc
hi
tec
t
ural
prin
c
i
pl
es
an
d
c
l
o
ud
s
ec
urit
y
att
ac
k
s
Evaluation Warning : The document was created with Spire.PDF for Python.
â—¼
IS
S
N: 16
93
-
6
93
0
T
E
L
KO
MNIK
A
V
ol
.
1
7
,
No
.
6
,
D
ec
em
b
er
20
19
:
28
1
2
-
2817
2814
wi
th
t
he
i
r
tec
hn
i
qu
es
th
at
c
an
m
i
n
i
m
i
z
e
th
e
ef
fec
ts
of
ma
l
i
c
i
ou
s
at
tac
k
s
(
mi
ti
ga
ti
o
n
tec
hn
i
qu
es
)
[
8
,
9
]
.
Iq
ba
l
A
hm
ed
et
a
l
.
i
ntro
du
c
es
green
IT
as
a
S
erv
i
c
e
(
G
aa
S
)
,
whi
c
h
i
s
i
mp
ortant
f
or
mo
d
ern
da
y
s
s
us
tai
na
bi
l
i
ty
c
on
c
ern
[
10
]
.
S
A
j
ou
da
n
i
na
n
et
a
l
.
s
ai
d
tha
t
fo
l
l
owi
ng
three
pa
r
a
me
t
ers
wer
e
th
e
mo
s
t
c
r
uc
i
al
(
a)
da
t
a
c
on
fi
de
nt
i
a
l
i
ty
(
b)
i
nte
grit
y
(
c
)
a
v
ai
l
a
bi
l
i
ty
[11
].
S
he
prop
os
ed
a
ne
w s
ec
uri
ty
mo
de
l
(
CI
A
)
[1
1]
,
f
or c
l
ou
d c
om
p
uti
ng
.
4.
F
ac
t
o
r
s Aff
ec
t
ing
Clou
d
S
ec
u
r
it
y
T
he
r
e
are
nu
me
r
ou
s
k
ey
fac
tors
whi
c
h
ma
y
a
ffe
c
t
c
l
ou
d
c
om
p
uti
ng
pe
r
for
ma
nc
e
be
c
au
s
e
i
t
i
s
s
urr
ou
nd
ed
by
ma
ny
tec
hn
ol
o
gi
es
,
for
ex
am
p
l
e,
l
oa
d
ba
l
an
c
i
ng
,
ne
tw
ork
,
c
on
c
urr
en
c
y
c
on
tr
ol
,
v
i
r
tua
l
i
z
ati
on
,
o
pe
r
at
i
n
g
s
y
s
tem
,
da
ta
ba
s
e,
me
m
ory
ma
n
ag
em
en
t
etc
[
12
].
Th
e
m
ai
n
k
ey
fac
tors
wh
i
c
h
are
af
fec
ti
ng
c
l
ou
d
pe
r
f
orm
an
c
e
are
s
ho
w
n
i
n
F
i
gu
r
e
3
.
T
he
s
ec
ur
i
ty
fac
tors
of
the
s
e
tec
hn
ol
o
gi
es
af
fec
ti
ng
th
e
c
l
o
ud
c
om
pu
ti
n
g
are
ap
pro
pria
te;
for
ex
am
p
l
e,
ne
twork
w
hi
c
h
c
o
nn
ec
ts
th
e
c
l
o
ud
c
o
mp
ut
i
n
g
to
th
e
o
ute
r
wor
l
d
ha
s
to
be
s
ec
ure
d.
V
i
r
tua
l
i
z
ati
on
c
on
c
ep
t
h
as
to
be
c
arr
i
e
d
ou
t
s
ec
urel
y
w
he
n
ma
pp
i
ng
w
i
th
the
ph
y
s
i
c
a
l
s
y
s
tem
s
.
Lo
a
d
ba
l
an
c
i
n
g
i
nv
o
l
v
es
the
h
an
d
l
i
n
g
o
f
i
nc
om
i
ng
r
eq
u
es
ts
tr
aff
i
c
w
hi
c
h
s
om
e
ti
me
s
ov
erl
oa
ds
the
s
erv
er. Da
ta
m
i
n
i
n
g a
l
g
orit
h
ms
c
an
b
e a
p
pl
i
e
d t
o c
op
e w
i
t
h
ma
l
i
c
i
ou
s
a
tta
c
k
s
.
F
i
gu
r
e
3.
F
ac
tors
a
ffe
c
ti
ng
c
l
ou
d s
ec
ur
i
ty
5.
P
o
ss
ible
Th
r
e
ats Reg
ar
d
ing
Clou
d
Co
mp
u
t
ing
Nowad
ay
s
c
l
ou
d
c
o
mp
ut
i
n
g
i
s
ge
tt
i
n
g
s
o
mu
c
h
po
pu
l
arit
y
th
at
i
t
i
s
i
n
t
he
l
i
me
l
i
g
ht
of
m
od
er
n
era.
A
l
on
g
wi
t
h
i
ts
hu
ge
b
en
ef
i
ts
c
l
ou
d
c
om
p
uti
ng
i
s
fac
i
ng
mu
c
h
s
ec
urit
y
i
s
s
u
es
whi
c
h
n
ee
d
c
on
s
i
de
r
a
bl
e
a
tte
n
ti
o
n
t
o
r
es
ol
v
e
t
he
m
for
th
e
b
ett
erment
of
th
i
s
s
erv
i
c
es
.
F
ol
l
owi
ng
are
the
m
aj
or c
on
c
erns
[1
3]:
-
O
uts
ou
r
c
i
ng
:
i
n
ou
ts
ou
r
c
i
n
g
the
da
t
a,
c
on
s
u
me
r
mi
g
ht
ge
t
l
os
e
the
c
on
tr
ol
.
S
o
me
k
i
nd
o
f
ap
pro
pria
t
e
m
ec
ha
n
i
s
m
i
s
ne
e
de
d
t
o
prev
e
nt
t
he
c
l
ou
d
s
erv
i
c
e
prov
i
de
r
(
CS
P
s
)
to
us
e
the
d
ata
ag
a
i
ns
t t
he
c
o
ns
e
nt
of
t
he
i
r
c
l
i
en
ts
.
-
Mu
l
t
i
te
na
nc
y
:
c
l
ou
d
i
s
a
s
ha
r
ed
p
oo
l
o
f
r
es
o
urc
es
.
P
r
ote
c
t
i
on
of
d
ata
m
us
t
b
e
t
ak
en
i
n
to
ac
c
ou
nt
w
hi
l
e p
r
ov
i
d
i
ng
the
mu
l
ti
-
te
na
n
t e
nv
i
r
on
m
en
t.
-
S
erv
i
c
e
L
ev
el
A
gre
em
e
nts
(
S
LA
)
:
a
c
l
ea
r
c
o
ntrac
t
b
etwe
e
n
th
e
c
on
s
um
er
an
d
prov
i
de
r
i
s
ne
ed
ed
. T
he
ma
i
n g
oa
l
of
a
greem
en
ts
i
s
t
o b
ui
l
d t
r
us
t.
-
Hete
r
og
en
ei
ty
:
di
f
feren
t
c
l
o
ud
prov
i
de
r
s
ha
v
e
di
ff
erent
me
c
ha
ni
s
m
of
da
t
a
protec
ti
on
wh
i
c
h
l
ea
ds
to
i
nte
grat
i
on
c
h
al
l
en
ge
s
.
-
S
erv
er
Downt
i
m
e:
do
w
nt
i
m
e
i
s
the
ti
me
i
n
whi
c
h
t
he
s
y
s
tem
s
tarts
r
es
po
nd
i
n
g
to
the
c
l
i
en
t
after
s
om
e
s
erv
i
c
e
fa
i
l
ure.
Downt
i
m
e
s
ho
u
l
d
be
k
ep
t
mi
n
i
m
i
z
ed
a
nd
po
wer
ba
c
k
up
s
mu
s
t
b
e
i
ns
ta
l
l
e
d t
o
k
ee
p
do
w
n
t
i
me
mi
n
i
m
um
.
Evaluation Warning : The document was created with Spire.PDF for Python.
T
E
L
KO
MNIK
A
IS
S
N: 1
69
3
-
6
93
0
â—¼
A
bri
ef
r
ev
i
ew:
s
ec
uri
ty
i
s
s
u
es
i
n c
l
ou
d
c
om
p
uti
ng
an
d
t
he
i
r
s
o
l
ut
i
on
s
(
Iq
ba
l
A
hm
ed
)
2815
-
B
ac
k
up
:
Dat
a
u
pl
o
ad
e
d
by
the
c
l
i
en
ts
,
s
h
ou
l
d
be
ba
c
k
ed
up
i
n
c
as
e
of
an
y
s
erv
i
c
e
fa
i
l
ure.
Cl
ou
d
s
e
l
l
er
s
ho
ul
d
me
nt
i
on
i
n
th
e
S
L
A
s
th
at
i
n
c
as
e
of
a
ny
d
i
s
as
ter
what
s
ho
u
l
d
be
the
r
em
ed
y
or
s
ol
u
ti
o
ns
to
s
uc
h
probl
em
s
.
T
he
r
e
i
s
v
e
r
y
r
are
c
ha
nc
e
of
who
l
e
s
y
s
tem
fa
i
l
ure
l
i
k
e f
l
o
od
e
tc
.
-
Data
Re
du
n
da
nc
y
:
Data
r
e
du
nd
an
c
y
i
s
a
s
i
tu
ati
on
i
n
whi
c
h
s
am
e
d
ata
i
s
be
i
ng
k
ep
t
o
n
two
di
ff
erent
pl
ac
es
.
In
c
as
e
of
c
l
ou
d
c
om
p
uti
ng
,
i
t
c
a
n
b
e
un
de
r
s
too
d
as
t
o
prov
i
d
e
c
op
i
es
of
s
am
e
da
ta,
s
y
s
tem
s
or
e
qu
i
pm
e
nt
to
t
he
c
l
i
e
nts
,
c
l
ou
d
prov
i
de
r
s
ho
ul
d
tr
y
to
k
ee
p
da
ta
r
ed
un
da
nc
y
m
i
ni
mu
m.
6.
S
o
lut
ion
s to
S
e
curity C
h
all
eng
es
in
Clo
u
d
Co
mp
u
t
ing
S
ec
urit
y
c
ha
l
l
e
ng
es
i
n
c
l
o
u
d
c
om
pu
t
i
ng
n
ee
d
to
be
a
dd
r
es
s
ed
proper
l
y
.
If
a
pp
r
op
r
i
at
e
s
ol
ut
i
on
s
are
no
t
be
i
ng
pro
v
i
de
d,
a
do
p
ti
o
n
of
c
l
ou
d
en
v
i
r
on
me
nt
be
c
o
me
s
mo
r
e
d
i
ffi
c
u
l
t.
A
pa
r
t
of
ad
op
ti
o
n,
da
t
a
tr
an
s
m
i
s
s
i
o
n
an
d
o
pe
r
at
i
on
t
en
d
to
b
ec
om
e
m
ore
ted
i
o
us
.
F
i
gu
r
e
4
el
a
bo
r
at
es
tha
t
d
ata
pro
tec
ti
on
an
d
pr
i
v
ac
y
i
s
the
mo
s
t
c
r
uc
i
a
l
fa
c
tor
am
on
g
al
l
[1
4
].
F
o
l
l
o
w
i
ng
ar
e
s
om
e
s
ol
ut
i
on
s
whi
c
h
n
ee
ds
to
be
c
on
s
i
de
r
ed
wh
i
l
e
c
o
n
s
i
de
r
i
ng
ab
o
ut
c
l
ou
d
c
om
pu
ti
ng
s
ec
urit
y
c
ha
l
l
en
g
es
.
F
i
gu
r
e
4.
D
ata
s
ec
ur
i
ty
c
ha
l
l
en
ge
s
6.1
. D
ata
E
n
cr
ypt
ion
E
nc
r
y
pti
o
n
i
s
s
ai
d
t
o
be
a
be
tte
r
ap
proac
h
r
e
ga
r
d
i
n
g
da
ta
s
ec
ur
i
ty
.
Data
s
h
o
ul
d
b
e
en
c
r
y
pte
d
b
efo
r
e
s
e
nd
i
ng
i
t
to
c
l
ou
d.
Dat
a
own
er
c
an
pe
r
mi
t
s
om
e
pa
r
ti
c
u
l
ar
m
e
mb
ers
to
h
av
e
ac
c
es
s
to
th
at
d
ata
[1
4
].
T
he
f
i
l
e
or
da
t
a
b
ei
ng
s
e
n
t
to
c
l
ou
d
s
h
ou
l
d
b
e
en
c
r
y
pte
d
fi
r
s
t
t
he
n
be
fore
s
tori
n
g
i
t
o
n
c
l
o
ud
i
t
s
ho
u
l
d
be
ag
a
i
n
en
c
r
y
pt
ed
by
t
he
c
l
ou
d
prov
i
de
r
;
the
pr
oc
es
s
i
s
k
no
wn
as
m
ul
t
i
s
tag
e
e
nc
r
y
pti
o
n.
I
t
h
as
be
en
ob
s
erv
e
d
th
at
c
o
mb
i
na
t
i
o
n
of
d
i
ffe
r
en
t
en
c
r
y
pti
o
n
al
g
orit
h
ms
prov
i
d
es
be
tt
er
en
c
r
y
pti
o
n
on
d
ata
.
E
x
pe
r
i
me
nt
al
r
es
u
l
ts
s
ho
w
th
at
R
S
A
+
ID
E
A
gi
v
es
the
h
i
g
he
r
p
erfor
ma
nc
e o
f
en
c
r
y
pti
o
n i
n s
ec
urin
g t
h
e d
ata
[
1
5,
16
].
6.2.
L
eg
al
Ju
r
isdi
ctio
n
W
he
n
i
t
c
o
me
s
to
u
nd
ers
ta
nd
an
d
an
al
y
s
e
th
e
l
e
ga
l
j
uris
di
c
ti
o
n
of
c
l
ou
d
c
o
mp
uti
n
g,
the
v
ery
ba
s
i
c
as
pe
c
ts
of
c
l
ou
d
en
v
i
r
o
nm
e
nt
c
om
pl
i
c
ate
t
he
da
t
a
prot
ec
ti
o
n,
for
ex
a
mp
l
e
pres
en
c
e
Evaluation Warning : The document was created with Spire.PDF for Python.
â—¼
IS
S
N: 16
93
-
6
93
0
T
E
L
KO
MNIK
A
V
ol
.
1
7
,
No
.
6
,
D
ec
em
b
er
20
19
:
28
1
2
-
2817
2816
of
i
nte
r
n
et,
v
i
r
tua
l
i
z
ati
on
,
dy
na
m
i
c
al
l
y
d
i
s
tr
i
b
ute
d
d
a
ta,
mu
l
ti
n
at
i
on
al
el
em
en
ts
.
Co
ns
um
ers
no
r
ma
l
l
y
d
o
n
ot
k
no
w
t
ha
t
where
t
he
i
r
da
t
a
r
es
i
d
es
i
n
c
l
ou
d
.
F
or
ex
a
mp
l
e,
a
c
l
i
e
nt
fr
om
Ind
i
a
ma
y
b
e
us
i
ng
a
s
erv
er
d
e
pl
oy
e
d
i
n
US
A
,
us
i
n
g
an
ap
p
l
i
c
at
i
on
w
hi
c
h
ha
s
be
e
n
d
ev
el
o
pe
d
i
n
J
ap
an
an
d
s
tori
n
g
h
i
s
c
r
uc
i
al
d
ata
at
a
d
ata
c
en
tr
e
wh
i
c
h
i
s
ph
y
s
i
c
a
l
l
y
l
oc
a
ted
i
n
S
wi
tz
er
l
an
d
[1
7
].
T
h
erefore
,
the
r
es
o
urc
e
al
l
oc
at
ed
to
t
he
c
on
s
u
me
r
s
s
ho
u
l
d
b
e
m
ark
ed
to
m
ak
e
s
ure tha
t
da
t
a i
s
s
e
gregat
e
d
[18
]
.
6.3.
D
istribu
t
ed D
enial of
S
er
vic
e (DD
o
S
)
Di
s
tr
i
bu
ted
Den
i
a
l
of
S
erv
i
c
e
i
s
a
k
i
n
d
of
att
ac
k
i
n
wh
i
c
h
att
ac
k
er
c
r
ea
tes
s
om
e
z
om
b
i
e
ma
c
hi
ne
by
i
n
fec
ti
ng
th
e
m
ac
hi
n
e
ov
er
the
i
nte
r
n
et
[1
9
-
22]
.
T
he
n
the
s
e
i
nf
ec
ted
ma
c
hi
ne
s
are
us
ed
t
o
at
tac
k
on
v
i
c
ti
m.
W
he
n
a
tta
c
k
s
/traffi
c
fr
om
s
o
ma
ny
i
n
fec
ted
m
ac
hi
n
e
s
are
d
i
r
ec
ted
towa
r
ds
on
e
v
i
c
ti
m,
i
ts
r
es
o
urc
e
l
i
k
e
C
P
U,
b
an
d
wi
d
th
a
nd
me
mo
r
y
s
tarts
ge
tt
i
ng
e
x
ha
us
ted
a
nd
pa
r
ti
c
u
l
ar
r
es
ou
r
c
e
b
ec
om
es
un
av
a
i
l
ab
l
e
for
c
o
ns
um
ers
.
T
o
c
op
e
w
i
th
thi
s
D
ee
pa
l
i
et
al
.
[1
9
]
ha
s
i
ntrod
uc
ed
a
l
ay
er
na
me
d
as
fo
g
l
ay
er
whi
c
h
s
i
tes
i
n
be
tw
ee
n
c
l
o
ud
s
erv
er
an
d
us
er.
A
l
l
th
e
r
e
qu
es
ts
ma
d
e
t
o
s
erv
er
are
fi
l
tere
d
thr
o
ug
h
thi
s
fog
l
ay
er
an
d
DDoS
att
ac
k
s
ge
t m
i
n
i
m
i
z
ed
.
6.4.
D
igit
al
S
ign
atu
r
e
Di
g
i
ta
l
s
i
g
na
ture
i
s
po
we
r
ful
to
ol
f
or
s
ec
urin
g
da
t
a
i
n
c
l
ou
d
c
om
p
uti
ng
[
2
3,
24
]
.
P
Rew
ag
a
d
et
al
.
[
25
]
ha
s
propos
e
d
a
s
ol
uti
on
us
i
ng
di
g
i
ta
l
s
i
g
na
tur
e
to
s
ec
ure
da
ta
al
o
ng
w
i
th
Di
ff
i
e
He
l
l
ma
n
k
ey
ex
c
ha
ng
e
w
i
th
A
E
S
en
c
r
y
pti
o
n
al
g
orit
h
m.
D
i
ff
i
e
He
l
l
ma
n
k
ey
ex
c
ha
ng
e
fac
i
l
i
ty
m
ark
s
i
t u
s
e
l
es
s
i
f th
e k
ey
i
s
h
ac
k
ed
i
n t
r
an
s
m
i
s
s
i
on
be
c
au
s
e
i
t
us
us
e
l
es
s
wi
th
ou
t
priv
ate
k
ey
of
us
er,
whi
c
h
i
s
c
on
fi
ne
d
to
l
eg
i
ti
ma
t
e
us
er
o
nl
y
.
T
hi
s
thre
e
-
way
me
c
h
an
i
s
m
w
hi
c
h
i
s
propos
e
d
i
n
t
ha
t
p
ap
er
ma
k
es
i
t
ha
r
de
r
to
ha
c
k
s
ec
urit
y
s
y
s
tem
,
the
r
ef
ore,
prot
e
c
ti
ng
th
e
da
ta
tha
t res
i
de
s
i
n c
l
ou
d.
7
.
Co
n
clus
ion
T
hi
s
pa
pe
r
ga
v
e
the
ov
erv
i
ew
of
c
l
ou
d
c
om
p
uti
ng
,
i
ts
v
ario
us
s
ec
urit
y
as
p
ec
ts
an
d
k
ey
fac
tors
wh
i
c
h
are
aff
ec
t
i
ng
the
c
l
ou
d
s
ec
ur
i
ty
.
C
l
o
ud
c
on
s
um
er
a
nd
prov
i
d
er
s
h
ou
l
d
be
s
ure
tha
t
the
i
r
c
l
o
ud
i
s
f
ul
l
y
s
ec
ure
a
nd
protec
te
d.
Cl
ou
d
c
om
pu
ti
ng
i
s
grow
i
n
g
i
n
ev
ery
i
nd
us
tr
y
ho
wev
er
i
t
s
uff
ers
fr
om
c
erta
i
n
i
s
s
u
es
r
eg
ard
i
ng
s
ec
urit
y
a
nd
protec
ti
on
w
hi
c
h
are
hu
r
d
l
e
i
n
i
ts
a
do
pt
i
o
n
wi
de
l
y
.
S
ol
uti
on
s
to
t
he
s
e
probl
em
s
ha
v
e
be
en
s
u
gg
es
te
d
wh
i
c
h
c
an
b
e
u
s
ed
for
be
t
ter
pe
r
forma
nc
e o
f c
l
o
ud
s
erv
i
c
es
i
n f
u
ture.
Ref
er
en
ce
s
[1
]
M
e
l
l
P
,
G
ra
n
c
e
T
.
Th
e
NIS
T
Def
i
n
i
t
i
o
n
o
f
Clo
u
d
Com
p
u
ti
n
g
.
NIST
s
p
e
c
i
a
l
p
u
b
l
i
c
a
t
i
o
n
8
0
0
-
145
.
Se
p
te
m
b
e
r
2
0
1
1
.
[2
]
Ra
s
h
i
d
Dar
Ab
,
Ra
v
i
n
d
r
a
n
D.
A
Com
p
re
h
e
n
s
i
v
e
St
u
d
y
on
Clo
u
d
C
o
m
p
u
ti
n
g
.
I
n
te
rn
a
ti
o
n
a
l
J
o
u
rn
a
l
o
f
Ad
v
a
n
c
e
Re
s
e
a
r
c
h
i
n
S
c
i
e
n
c
e
a
n
d
En
g
i
n
e
e
ri
n
g
.
2
0
1
8
;
7
(4
):
2
3
5
-
2
4
2
.
[3
]
M
e
l
l
P
,
G
ra
n
c
e
T
.
Th
e
NIST
D
e
fi
n
i
ti
o
n
o
f
Clo
u
d
Com
p
u
ti
n
g
,
v
e
rs
i
o
n
1
5
.
Nat
i
o
n
a
l
In
s
ti
tu
te
o
f
Sta
n
d
a
r
d
s
a
n
d
T
e
c
h
n
o
l
o
g
y
(NIS
T),
I
n
fo
r
m
a
ti
o
n
T
e
c
h
n
o
l
o
g
y
L
a
b
o
ra
to
r
y
.
2
0
1
1
.
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